Acyl-coenzyme A: cholesterol- acyl-coenzyme A:1,2-diacylglycerol acyltransferase and phosphatidate phosphorylase activities in liver microsomes from nephrotic rats.

The lipid components of very low density lipoproteins (VLDL) were significantly elevated in the nephrotic rats. Also the nephrotic VLDL particles had a significantly higher ratio of surface lipids (FC + PL) to core lipids (TG + CE) probably indicating production of smaller sized VLDL in the nephrotic rats. Electron microscopy showed VLDL particles with a reduced mean size in the nephrotic rats. The activities of VLDL core lipid synthesizing enzymes were evaluated in experimental nephrotic syndrome. In addition, the effects of exogeneous cholesterol, 25-OH-cholesterol and low density lipoprotein (LDL) on the acyl-coenzyme A: cholesterol acyltransferase (ACAT) activity were investigated as well. ACAT activity in nephrosis was normal, but stimulated to varying extents in the presence of these factors. On the other hand, the acylcoenzyme A:1,2-diacylglycerol acyltransferase (ADGAT) and phosphatidate phosphorylase-activities were significantly increased in the nephrotic rats. The microsomal cholesterol (free and ester) and phospholipid concentrations were normal but the triglyceride level was significantly reduced in the experimental group. We speculate that an excess production of smaller-sized VLDL particles due to altered activities of microsomal lipid synthesizing enzymes may occur in puromycin amino nucleoside induced-nephrotic rats.